1. Field of the Invention
This invention relates to a speaker diaphragm and a method of manufacturing the speaker diaphragm.
The present application claims priority from Japanese Application No. 2001-103117, the disclosure of which is incorporated herein by reference for all purposes.
2. Description of the Related Art
Conventionally, as the base materials for forming speaker diaphragms, flammable materials, such as paper, a variety of resins, fabrics or the like, are typically employed because of their lightweight properties and low cost.
Accordingly, when an abnormal current flows through the speaker or when abnormal heating occurs on the periphery of the speaker, there may be cases where an accidental fire originates in the diaphragm, which has the largest area among the parts making up the speaker, and spreads.
Paper, woven fabric and non-woven fabric are most commonly used due to they having the lightest weight and the lowest cost among conventional materials for diaphragms, but they typically are so high in hygroscopicity or water-absorption properties that after the paper, woven fabrics or non-woven fabrics absorbs moisture or water, the binding between fibers making up the material decrease, resulting in a decrease in strength of the material.
Therefore, a problem is that the paper, woven fabric and non-woven fabric are unfit for diaphragms of speakers placed in harsh use-environments where water is directly poured on it or in humid surroundings, e.g., a vehicle-mounted speaker.
Moreover, in order to enhance extension of a high-pitched tone in the speaker, the speaker needs a hard and lightweight diaphragm.
With the conventional diaphragms using paper, the diaphragm is made to be hard by mixing a paper pulp with fibers, such as carbon fiber, or an inorganic substance, such as mica, as a filler in making paper or by impregnating paper with resin.
However, though mixing the paper pulp with the filler or impregnating paper with resin can provide a hard diaphragm to a certain extent, this has not been able to provide a diaphragm satisfying the requirements for a tweeter serving as a speaker designed specially for high frequency.
As the diaphragms for the tweeter, conventionally, a variety of materials are used: for example, metal such as aluminium, beryllium and titanium, a resin film made of polyimide or the like, and carbon.
However, there is a problem that the metal is heavy in weight and the resin film made of polyimide or the like, and carbon are high in cost.
The present invention has been made to solve the problems associated with the conventional speaker diaphragms as described above.
It is therefore a first object of the present invention to provide a speaker diaphragm having water resistance and humidity resistance without the possibility of an accidental fire, and having a high rigidity with light weight.
Further, it is a second object of the present invention to provide a method of manufacturing a speaker diaphragm allowing the attainment of the first object.
To attain the first object, a speaker diaphragm according to a first aspect of the present invention has the feature of including a material resulting from combining a ceramic-type-coating agent with a fiber-type material.
The speaker diaphragm according to the first aspect is formed by various methods; for example, the fiber-type material is formed into an arbitrary shape of the diaphragm, and then combined with the ceramic-type-coating agent through impregnation or coating; the ceramic-type-coating agent is mixed into the beaten fiber-type material and then processed into paper to form an arbitrary shape of the diaphragm; the fiber-type material is impregnated or coated with the ceramic-type-coating agent, then beaten, and then processed into paper to form an arbitrary shape of the diaphragm.
According to the first aspect, the covering of the surface of the fiber-type material, which is a base material of the speaker diaphragm, with a ceramic film causes the speaker diaphragm to be incombustible or flame-retardant. This prevents the speaker from bursting into flames as a result of the diaphragm catching fire.
Further, the ceramic film formed by the ceramic-type-coating agent having been combined with the fiber-type material increases the rigidity of the diaphragm. Hence, it is possible to significantly improve the endurance against impact even when the diaphragm is placed in a vehicle-mounted speaker, for example.
Still further, the ceramic film formed by the ceramic-type-coating agent having been combined with the fiber-type material improves humidity resistance and water resistance and strengthens the binding between the fibers. Hence, the environmental resistance including thermal resistance is improved to allow the diaphragm to be used in speakers which are placed in harsh environments where water is directly poured on it or the temperature and humidity are high, as in the case of a vehicle-mounted speaker, for example.
Further, according to the first aspect, the impregnation or coating of a fiber-type material, such as paper pulp, or a cloth material, such as glass cloth, with the ceramic-type-coating agent allows the provision of the lightweight and high-rigid diaphragm at low cost.
The use of ceramic for the diaphragm allows a significant extension of the high frequency characteristics of the speaker.
To attain the first object, a speaker diaphragm according to a second aspect of the present invention has the feature, in addition to the configuration of the first aspect, that the ceramic-type-coating agent is a ceramic-type-coating agent made up of at least one item selected from the group consisting of an alkoxy metal, a hydrolysate of the alkoxy metal and a partial condensation product of the hydrolysate.
With the speaker diaphragm according to the second aspect, after the ceramic-type-coating agent made up of at least one item selected from the group consisting of an alkoxy metal, a hydrolysate of the alkoxy metal and a partial condensation product of the hydrolysate, is applied to the fiber-type material such as paper or resin, the ceramic-type-coating agent is hardened at room temperatures or by low-temperature heating, and undergoes hydrolysis and a polycondensation reaction, to form a ceramic film which is noncombustible and outstanding in thermal resistance and weather resistance, and has a high water repellency and water proofing property due to its high density, and also electrical-insulation properties, and shock impact resistance due to its high degree of hardness.
To attain the first object, a speaker diaphragm according to a third aspect has the feature, in addition to the configuration of the first aspect, that the ceramic-type-coating agent is a ceramic-type-coating agent made up of at least one item selected from the group consisting of mixtures of an alkoxy metal and a silicone varnish.
With the speaker diaphragm according to the third aspect, the ceramic-type-coating agent made up of at least one item selected from the group consisting of mixtures of an alkoxy metal and a silicone varnish, which is combined with the fiber-type material serving as the base material of the diaphragm, is hardened at room temperatures or by low-temperature heating, to form a ceramic film which has noncombustibility, thermal resistance, weather resistance and electrical-insulation properties, and is outstanding in damage resistance due to its high degree of hardness.
To attain the first object, a speaker diaphragm according to a fourth aspect has the feature, in addition to the configuration of the first aspect, that the ceramic-type-coating agent is a ceramic-type-coating agent made up of at least one item selected from the group consisting of mixtures of alkali metal salt and silicone varnish emulsion.
With the speaker diaphragm of the fourth aspect, metal alkoxide and metal hydroxide are used for the ceramic-type-coating agent to be combined with the fiber-type material serving as the base material of the diaphragm.
The above ceramic-type-coating agent includes a ceramic-type-coating agent formed of metal alkoxide, metal hydroxide, and a colloidal or fine-particulate inorganic substance.
The above ceramic-type-coating agent is hardened at room temperatures or by low-temperature heating, to form a ceramic film which has noncombustibility, thermal resistance, weather resistance and electrical-insulation properties, and is outstanding in damage resistance due to its high degree of hardness.
To attain the first object, a speaker diaphragm according to a fifth aspect has the feature, in addition to the configuration of the first aspect, that the ceramic-type-coating agent is a ceramic-type-coating agent including a colloidal inorganic substance or a fine-particulate inorganic substance having favorable heat-emission properties. The above ceramic-type-coating agent is combined with the fiber-type material serving as the base material of the diaphragm, to form a ceramic film having noncombustibility, thermal resistance, weather resistance and electrical-insulation properties, and be outstanding for damage resistance due to its high degree of hardness.
A speaker diaphragm according to a sixth aspect has the feature, in association with the fifth aspect, that the colloidal inorganic substance or the fine-particulate inorganic substance having favorable heat-emission properties is an impalpable powder of metal oxide having the property of converting heat into infrared radiation for emission.
To attain the first object, a speaker diaphragm according to a seventh aspect has the feature, in addition to the configuration of the first aspect, that a fine-particulate inorganic substance is adhered to the surface of the speaker diaphragm. This allows adjustment of the vibration frequency of the speaker diaphragm, sound reflection and sound absorption for improving the sound quality, and the setting of a desired sound quality.
A speaker diaphragm according to an eighth aspect has the feature, in association with the seventh aspect, that the fine-particulate inorganic substance is a fine-particulate inorganic substance consisting of at least one item selected from the group consisting of a particulate metal, metal oxide, metal hydroxide, metal nitride, and metal carbide.
To attain the first object, a speaker diaphragm according to a ninth aspect has the feature, in addition to the configuration of the first aspect, that the ceramic-type-coating agent is a ceramic-type-coating agent including a scaly inorganic substance or a short-fibrous whisker inorganic substance. The ceramic-type-coating agent is combined with the fiber-type material serving as the base material of the diaphragm, to form a ceramic film having noncombustibility, thermal resistance, weather resistance and electrical-insulation properties, and outstanding in damage resistance due to its high degree of hardness.
A speaker diaphragm according to a tenth aspect has the feature, in association with the ninth aspect, that the scaly inorganic substance or the short-fibrous whisker inorganic substance is a fine-particulate inorganic substance consisting of at least one item selected from the group consisting of a particulate metal, metal oxide, metal hydroxide, metal nitride, and metal carbide.
To attain the first object, a speaker diaphragm according to an eleventh aspect has the feature, in addition to the configuration of the first aspect, that the fiber-type material is either a paper-pulp based material, a woven fabric or a non-woven fabric.
With the speaker diaphragm of the eleventh aspect, the paper-pulp based material is beaten and then processed into paper or the woven fabric or non-woven fabric is pressed, for formation into an arbitrary shape of the diaphragm.
Due to the combining of the ceramic-type-coating agent with the paper-pulp based material, woven fabric or non-woven fabric, even when the diaphragm is formed from a fiber-type material which is a flammable base material, it is possible for the diaphragm to maintain noncombustibility or flame retardancy, water resistance, and humidity resistance.
To attain the second object, a method of manufacturing a speaker diaphragm according to a twelfth aspect of the present invention includes the step of forming a material resulting from combining a ceramic-type-coating agent with a fiber-type material into an arbitrary shape of the speaker diaphragm.
According to the method of manufacturing the speaker diaphragm of the twelfth aspect, the covering of the surface of the fiber-type material, which is a base material of the speaker diaphragm, with a ceramic film causes the speaker diaphragm to be incombustible or flame-retardant. This prevents the speaker from bursting into flames as a result of the diaphragm catching fire.
Further, the ceramic film formed by the ceramic-type-coating agent having been combined with the fiber-type material increases the rigidity of the diaphragm. Hence, it is possible to significantly improve the endurance against impact even when the diaphragm is placed in a vehicle-mounted speaker, for example.
Still further, the ceramic film formed by the ceramic-type-coating agent having been combined with the fiber-type material improves humidity resistance and water resistance and strengthens the binding between the fibers. Hence, the environmental resistance including thermal resistance is improved to allow the diaphragm to be used in speakers which are placed in harsh environments where water is directly poured on it or the temperature and humidity are high, as in the case of a vehicle-mounted speaker, for example.
Further, according to the twelfth aspect, the impregnation or coating of a fiber-type material, such as paper pulp, or a cloth material, such as glass cloth, with the ceramic-type-coating agent allows the provision of the lightweight and high-rigid diaphragm at low cost.
The use of ceramic for the diaphragm allows a significant extension of the high frequency characteristics of the speaker.
To attain the second object, a method of manufacturing a speaker diaphragm according to a thirteenth aspect of the present invention, in addition to the configuration of the twelfth aspect, includes the steps of: forming the fiber-type material into an arbitrary shape of the diaphragm; and impregnating or coating the fiber-type material, formed into the arbitrary shape of the diaphragm, with the ceramic-type-coating agent, in order to manufacture the speaker diaphragm.
According to the method of manufacturing the speaker diaphragm of the thirteenth aspect, for the formation into the shape of the diaphragm, when the fiber-type material serving as the base material is paper, the pulp or beaten paper-fibers are processed into paper. When the fiber-type material is woven fabric or non-woven fabric, the fabric sheet is pressed. The fiber-type material formed into the required shape of the diaphragm is impregnated or coated with the ceramic-type-coating agent.
Then the ceramic-type-coating agent with which the shaped fiber-type material is impregnated or coated is solidified at room temperatures or by low-temperature heating to form a ceramic film on the surface of the fiber-type material.
To attain the second object, a method of manufacturing a speaker diaphragm according to a aspect, in addition to the configuration of the twelfth aspect, includes the steps of: mixing the ceramic-type-coating agent into the fiber-type material in a separated fiber state before shaping; and processing the fiber-type material, mixed with the ceramic-type-coating agent, into paper for formation into an arbitrary shape of a diaphragm of a speaker in order to manufacture the speaker diaphragm.
According to the method of manufacturing the speaker diaphragm of the aspect, the ceramic-type-coating agent which is mixed into the fiber-type material and then is processed together with the fiber-type material into paper, is solidified at room temperatures or by low-temperature heating to form a ceramic film on the surface of the fiber-type material having the shape of the diaphragm.
To attain the second object, a method of manufacturing a speaker diaphragm according to a fifteenth aspect, in addition to the configuration of the twelfth aspect, includes the steps of: impregnating or coating the fiber-type material with the ceramic-type-coating agent; beating the fiber-type material impregnated or coating with the ceramic-type-coating agent; and processing the beaten fiber-type material into paper for formation into an arbitrary shape of a diaphragm of a speaker in order to manufacture the speaker diaphragm.
According to the method of manufacturing the speaker diaphragm of the fifteenth aspect, the ceramic-type-coating agent with which the fiber-type material is impregnated or coated is solidified at room temperatures or by low-temperature heating to produce a ceramic film. The resulting fiber-type material is beaten and then the diaphragm of the required shape is formed by the fibers on which the ceramic film is produced.
These and other objects and features of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings.